The invention relates generally to media storage systems for handling and storing data cartridges, and more specifically, to a data cartridge detector for use therewith.
Media storage systems are well known in the art and are commonly used to store data cartridges at known locations and to retrieve the desired data cartridges so that data may be written to and/or read from the data cartridges. Such media storage systems are often referred to as autochangers or library storage systems.
A typical autochanger or media storage system may include one or more different types of cartridge-receiving devices for holding the various data cartridges. For example, one type of cartridge-receiving device may comprise an individual cartridge storage location (e.g., for holding a single data cartridge) or a cartridge storage rack or xe2x80x9cmagazinexe2x80x9d (e.g., for holding a plurality of data cartridges). The cartridge storage location or racks serve to provide storage locations for the data cartridges and are commonly arranged so that they form one or more vertical stacks, although other arrangements are possible. Another type of cartridge-receiving device may comprise one or more cartridge read/write devices for reading data from and/or writing data to the data cartridges contained in the autochanger. The cartridge read/write device(s) may be located at any convenient position within the media storage system.
The autochanger or media storage system may also be provided with a cartridge handling system for transporting the data cartridges between the various cartridge-receiving devices. For example, the cartridge handling system may transport the data cartridges between the cartridge storage location or racks and the cartridge read/write device. A typical cartridge handling system may include a cartridge engaging assembly or xe2x80x9cpickerxe2x80x9d for engaging the various data cartridges contained in the cartridge-receiving devices. In addition, the cartridge handling system also typically includes a positioning device for moving the cartridge engaging assembly among the various cartridge-receiving devices.
Autochangers or media storage systems of the type described above are usually connected to a host computer system which may access or store data on the data cartridges. For example, if the host computer system issues a request for data contained on a particular data cartridge, a control system associated with the autochanger actuates the positioning system to move the cartridge engaging assembly along the cartridge storage locations until the cartridge engaging assembly is positioned adjacent the desired data cartridge. The cartridge engaging assembly may then remove the data cartridge from the cartridge storage location and carry it to the cartridge read/write device. Once properly positioned adjacent the cartridge read/write device, the cartridge engaging assembly may insert the selected data cartridge into the cartridge read/write device so that the host computer may thereafter read data from or write data to the data cartridge. After the read/write operation is complete, the cartridge engaging assembly may remove the data cartridge from the cartridge read/write device and return it to the appropriate cartridge storage location.
In use, it is often necessary to know whether a data cartridge is present in the cartridge engaging assembly. At start-up, for example, it is necessary to know whether there is already a data cartridge in the cartridge engaging assembly. If a data cartridge is already present in the cartridge engaging assembly, the data cartridge may first need to be returned to an appropriate cartridge-receiving device before the media storage system will be ready for service. In addition, if a data cartridge is to be retrieved from a cartridge-receiving device, it is necessary to know whether the data cartridge was successfully engaged before moving the cartridge engaging assembly to the read/write device for access thereto, or whether another attempt is required to successfully engage the data cartridge.
One solution for determining whether a data cartridge is present in the cartridge engaging assembly is to position the cartridge engaging assembly at one of the read/write devices, and unload the contents, if any, into the read/write device. The read/write device may then be used to read the data cartridge to determine whether there was indeed a data cartridge present in the cartridge engaging assembly. Where the read/write device is unable to read and/or write to the data cartridge, this may indicate that the cartridge engaging assembly was empty. However, it may also indicate that the unload was unsuccessful, and that the data cartridge is still in the cartridge engaging assembly. In addition, according to this solution an unsuccessful retrieval goes undetected until the cartridge engaging assembly is positioned at the read/write device and there is nothing to unload. Thus, the cartridge engaging assembly must return to the cartridge storage location or rack and again attempt to retrieve the data cartridge.
Another solution is to provide a mechanical switch within the cartridge engaging assembly. As such, when a data cartridge passes into or out of the cartridge engaging assembly, the switch is thrown (e.g., xe2x80x9conxe2x80x9d or xe2x80x9coffxe2x80x9d). As such, the switch position indicates whether a data cartridge is present within the cartridge engaging assembly. However, mechanical switches have finite tolerances. For example, a slightly smaller data cartridge may pass into or out of the cartridge engaging assembly without triggering the switch. In addition, mechanical switches are prone to physical wear. As such, the switch may provide false information, indicating that a data cartridge is present when it is not, or vice versa.
Yet another solution is to provide the cartridge engaging assembly with suitable servo-electronics, and a known object against which the cartridge engaging assembly attempts to unload its contents, if any. As the cartridge engaging assembly attempts to unload against the known object, the opposing force is measured. Where a data cartridge is present within the cartridge engaging assembly, the opposing force is greater than when the cartridge engaging assembly is empty, thus indicating the presence of a data cartridge therein. However, this solution requires expensive and sensitive servo-electronics that are capable of measuring and processing the opposing forces. In addition, it is time consuming to position the cartridge engaging assembly adjacent the known object, perform the test, and process the results.
System and apparatus for determining the presence of a data cartridge in a cartridge engaging assembly according to one embodiment of the invention may comprise a signal emitter positioned adjacent the cartridge engaging assembly. A signal detector may be mounted to the cartridge engaging assembly to detect a signal from the signal emitter. The signal detector generates output to indicate whether a data cartridge is present in the cartridge engaging assembly based on the detected signal.
Also disclosed is a method for determining the presence of a data cartridge in a cartridge engaging assembly that may comprise the steps of: emitting a signal into the cartridge engaging assembly; detecting the emitted signal; and generating output to indicate whether the data cartridge is present in the cartridge engaging assembly based on the detected signal.